This invention relates to glass compositions and methods of making the same. More particularly, this invention relates to glass compositions including at least erbium (Er) and holmium (Ho), which have low light transmittance in the UV (ultraviolet) and IR (infrared) ranges and high light transmittance in the visible range. Such glass compositions are useful, for example, in windows and windshields in the automotive industry and also in architectural applications. Glasses herein may be grey, or otherwise colored.
The automotive industry, for a number of years, has desired glass having grey color (sometimes called xe2x80x9cneutral greyxe2x80x9d) for automotive window applications. At the same time, it is also desirable for transmission in the UV and/or IR ranges of the light spectrum to be minimized. Moreover, certain Governmental regulations in the automotive industry have been known to require that visible light transmittance be at least 70% in certain vehicular windows when provided by the original equipment manufacturer of the vehicle (e.g. GM, Ford, Chrysler etc.) in the U.S.A. Accordingly, there exists a need in the automotive industry for a glass which achieves these properties (a similar need may also exist in other industries such as the architectural glass industry).
A glass window or other glass article is said to have the desirable color xe2x80x9cgreyxe2x80x9d when it has a dominant wavelength of from 435 nm to 570 nm (this dominant wavelength range defines the color xe2x80x9cgreyxe2x80x9d herein). Moreover, grey glass often has an excitation purity of less than about 4.5%. In certain embodiments, it may be preferable to have a dominant wavelength of from 470 nm to 570 nm, or even from 480-560 nm, with purity of from about 0.2 to 4.5%.
While glass having xe2x80x9cgreyxe2x80x9d color is often desirable, there sometimes also exists a need or desire to achieve certain levels of light transmission defined conventionally by:
Lta as visible light transmission,
UV as ultraviolet light transmission, and
IR as infrared light transmission.
Glass thickness ranges of from about 1-6 mm, more preferably from about 3-4 mm, are typically used when measuring the aforesaid characteristics. These thickness ranges are generally recognized as conventional thicknesses for glass sheets made by the float glass process, as well as recognized thickness ranges in the automotive industry.
For automotive windows (including windshields) it is often desirable for glass to have one or more of the following characteristics at any or all of the aforesaid thicknesses:
Lta: at least about 70%
UV: no greater than about 52%, more preferably no greater than 50%
IR: no greater than about 46%, more preferably no greater than 42%
Classically formulated grey glasses often include low levels of iron (i.e., less than 0.2% total iron) along with cobalt and nickel oxides. Unfortunately, while this type of glass may achieve satisfactory coloration in certain instances, it typically suffers from undesirable solar characteristics. Certain nickel-free grey glasses combine selenium (Se) and cobalt (Co) oxide with iron oxide, but also suffer from poor solar performance characteristics.
Certain known green solar control float glasses are formulated so as to achieve desirable solar characteristics due in large part to their use of large quantities of total iron (e.g., 0.60 to 0.84% total iron). Unfortunately, the green coloration of such glasses does not always harmonize well with certain exterior automotive paints and sometimes affects vehicle interiors when viewed through the glass.
In view of the above, it is apparent that there exists a need in the art for a new glass composition which overcomes the above problems while achieving one or more of desired grey color and desired solar management property(ies) of the particular application in which it is to be used.
An object of this invention is to provide a grey glass (i.e., having a dominant wavelength of from 435 nm to 570 nm) including a colorant portion which may include at least from 0.20 to 2.50%, by weight, erbium oxide (e.g., Er2O3), from about 0.10 to 0.90%, by weight total iron (expressed as Fe2O3); and from about 0.05 to 1.60%, by weight, holmium oxide (e.g., Ho2O3); and from about 0.10 to 2.0%, by weight, yttrium oxide (e.g., Y2O3). The combination of erbium oxide, iron oxide, holmium oxide, and yttrium oxide provides for desirable color and/or solar characteristics in different embodiments of this invention.
In certain example embodiments of this invention, one or more of the above listed needs and/or objects is/are fulfilled by providing a glass comprising:
In other example embodiments of this invention, one or more of the above-listed objects and/or needs is fulfilled by providing a grey glass comprising:
a base glass portion comprising:
and a colorant portion consisting essentially of:
wherein the grey glass has a dominant wavelength in the range of from 435 nm to 570 nm.
In certain embodiments, the glass may be grey in color and have an excitation purity (Pe) of no greater than about 4.5%.
In certain exemplary embodiments, the glass or glass composition is substantially free of cerium and/or nickel.
While grey color is preferred in certain embodiments, this invention is not so limited. Colorant portions herein may be used in conjunction with other glass colors in alternative embodiments of this invention.
Glasses according to different embodiments of this invention may be used, for example, in the automotive industry (e.g., windshields, backlites, side windows, etc.), in architectural applications, and in other suitable applications. Such glasses may be grey, or otherwise colored in different embodiments of this invention.
Certain glasses according to this invention utilize soda-lime-silica flat glass as their base composition/glass, to which is added certain ingredients making up a unique colorant portion. An exemplary soda-lime-silica base glass according to certain embodiments of this invention, on a weight percentage basis, includes the following basic ingredients:
It is noted that in certain preferred embodiments of this invention, the Yttrium oxide (Y2O3) is added to the base glass along with the colorants. However, because Y2O3 is knows to be essentially colorless in glass, it is listed and considered herein as part of the base glass as opposed to the colorant portion. In certain preferred embodiments of this invention, the glass composition (before and after the melt) includes from about 0.10 to 2.0% Y2O3, more preferably from about 0.10 to 1.0% Y2O3, and even more preferably from about 0.10 to 0.6% Y2O3.
Other minor ingredients, including various conventional and refining aids, such as SO3, carbon, gypsum, CaSO4 and the like may also be included in the base glass. In certain embodiments, for example, glass herein may be made from batch raw materials silica sand, soda ash (or NaOH as a soda source), dolomite, limestone, with the use of salt cake (SO3) and/or Epsom salts (e.g., about a 1:1 combination of both) as refining agents. Reducing agent(s) such as Si (metallic), Si, silicon monoxide, SiO, sucrose, and/or carbon may also be used. Preferably, soda-lime-silica base glasses herein include by weight from about 10-15% Na2O and from about 6-12% CaO. While a soda-lime-silica base glass set forth above is preferred in certain embodiments of this invention, this invention is not so limited. Thus, other base glasses (e.g., borosilicate glass) may instead be employed in alternative embodiments.
To the base glass (e.g., see Table 1 above), the instant invention adds a colorant portion which may cause the resulting glass to be grey in color (e.g., dominant wavelength of from 435 nm to 570 nm) and/or achieve desirable solar management properties (e.g., low UV and IR transmission coupled with high visible transmission). In certain preferred embodiments, the resulting glass is grey in color and has a dominant wavelength of from 480 nm-560 nm (nanometers). Moreover, the resulting glass preferably has an excitation purity (Pe) no greater than about 4.5%, and most preferably from 0.2% to 4.5%.
In certain embodiments of this invention, an exemplary colorant portion that is added to the base glass is substantially free of cerium and nickel (i.e., no more than 0.0030% Ce, CeO, and/or CeO2, and no more than 0.0010% Ni and/or NiO), and is characterized in final glasses as set forth in Table 2 below (in terms of weight percentage of the total glass composition):
It should be appreciated that small amounts of other materials (e.g., refining aids, melting aids, and/or impurities) may be present in the glass such as chromium, manganese, molybdenum, tin, chlorine, zinc, zirconium, Si, sulfate, fluorine, lithium and strontium, without taking away from the purpose(s) and/or goal(s) of the instant invention. It is also noted that up to about 2.0% total iron may be used in certain embodiments of this invention.
The total amount of iron present in the glass and in the colorant portion thereof is expressed herein in terms of Fe2O3 in accordance with standard practice. This, however, does not imply that all iron is actually in the from of Fe2O3. Likewise, the amount of iron in the ferrous state is reported herein as FeO, even though all ferrous state iron in the glass may not be in the form of FeO. The proportion of the total iron in the ferrous state (i.e., FeO) is used to determine the redox state of the glass, and is expressed as the ratio FeO/Fe2O3, which is the weight percentage (%) of iron in the ferrous state (expressed as FeO) divided by the weight percentage (%) of total iron (expressed as Fe2O3). Thus, Fe2O3 herein means total iron and FeO means iron in the ferrous state. According to certain embodiments of this invention, the colorant portion of the glass composition herein is characterized by a redox value (i.e., FeO/Fe2O3) of from 0.10 to 0.25, more preferably from 0.12 to 0.20.
Moreover, it is noted that glass according to this invention is often made via the known float process in which a tin bath is utilized. It will thus be appreciated by those skilled in the art that as a result of forming the glass on molten tin in certain exemplary embodiments, small amounts of tin or tin oxide may migrate into surface areas of the glass on the side that was in contact with the tin bath during manufacture (i.e., typically, float glass may have a tin oxide concentration of 0.05% or more (wt.) in the first few microns below the surface that was in contact with the tin bath).
Glasses of this invention, as stated above, may in certain non-limiting embodiments achieve a true grey or neutral grey color. Such a true xe2x80x9cgreyxe2x80x9d color is best s defined, as aforesaid, by referring to: (1) xe2x80x9cdominant wavelengthxe2x80x9d, and/or (2) xe2x80x9cexcitation purity.xe2x80x9d Other colors are also possible in other embodiments of this invention. In certain embodiments, glasses herein include one or more of the following color/solar characteristics when measured at a nominal thickness of from about 1 mm-6 mm (and preferably for most uses, at about 3 mm-4 mm):
When used in the automotive market for windows and/or windshields that must conform to certain minimal visible light transmission properties, certain example glass articles of this invention (e.g., at 3 mm thicknesses for purposes of reference) preferably have an Lta of at least 65%, more preferably of at least about 70% and, in certain embodiments of least about 72%, and in still further instances at least about 75%; and/or an IR transmission percentage (%) of no greater than 46%. Additionally, in certain exemplary embodiments, glasses herein have a UV transmission percentage (%) of no greater than about 52%, more preferably no greater than about 50%, and sometimes no greater than 46%. These optical characteristics relate to example embodiments only, and are not limiting upon the invention as a whole unless specifically claimed herein.
The glasses of this invention achieve the above unique characteristics (i.e., desired color in combination with desired solar management properties, e.g., Lta, UV, IR) in base glasses (e.g., silicate glasses such as soda-lime-silica, or borosilicate glasses) through the use of the unique colorant portions discussed herein. Erbium acts as a pink colorant, holmium as a pale yellow colorant, and the FeO aspect of the total iron acts as a blue colorant. As discussed above, selenium and cobalt may be utilized in the colorant portion for coloration purposes to achieve the desired grey color.
With regard to Se, in certain embodiments Se may be introduced into the glass batch in amounts of, for example, from 5-20 ppm. In order to increase retention of Se and to improve homogeneity of the glass through a more uniform Se distribution in the melt, compositions of this invention may use various sources of Se, such as sodium and/or calcium selenites, iron and/or cobalt selenides, and/or metallic Se powder. Moreover, while Se often combines with iron as iron selenide (FeSe) in glass to produce brown color, and does so in certain embodiments of this invention, selenium is referred to in the colorant portion herein as xe2x80x9cSexe2x80x9d which is meant to include, for example, its state as Se as well as other states in glass such as FeSe. While the use of Se is preferred in the colorant portion as discussed above, it is noted that in some embodiments Se need not be present.
Regarding cobalt (Co), this blue colorant may be added to the glass batch in amounts of, for example, 10-30 ppm. Moreover, it is believed that much of the cobalt in the glass is in the oxide state of Co3O4. However, other oxide states of CoO are also possible in glasses according to this invention. Thus, unless expressly stated to the contrary, the terms cobalt oxide, CoO and Co3O4 as used herein include not only cobalt in this/these particular oxide state(s), but also include(s) cobalt which may be present in other oxide state(s).
Holmium oxide acts as a pale yellow colorant. Moreover, it is believed that much of the holmium in the glass is in the oxide state of Ho2O3. However, other oxide states of HoO are also possible in glasses according to this invention. Thus, unless expressly stated to the contrary, the terms holmium oxide, HoO and Ho2O3 as used herein include not only holmium in this/these particular oxide state(s), but also include(s) holmium which may be present in other oxide state(s). Also, with regard to Er, unless expressly stated to the contrary, the terms erbium oxide, ErO and Er2O3 as used herein include not only Er in this/these particular oxide state(s), but also include(s) Er which may be present in other oxide state(s). The same is true of other oxides herein, including but not limited to yttrium oxide.
Colorant elements Ho, Er, Tm, Yb and Lu are all lanthanides or rare earth elements. Thus, as can be seen herein, in certain preferred embodiments a plurality of different lanthanides (or rare earth elements) are used in the glass composition together with iron in order to achieve the desired glass color. This is advantageous in that lanthanides are often grouped together when mined, and thus the ability to use multiple lanthanides together as a colorant portion is more cost efficient than previous methods of adding colorants such as Er. For example and without limitation, a three element concentrate including oxides of Er, Ho and Y may be added to the base glass in order to color the same as will be explained in the examples below (regardless of when Y is added to the glass composition, whether or not along with Er and Ho, it is considered part of the base glass because it is essentially colorless and does not act as a colorant herein). In other embodiments, a different plurality of rare earth oxides may be added to the base glass. In some embodiments of this invention three or more lanthanides combine with at least iron in order to achieve the desired glass color and/or solar characteristics.
For purposes of example only, and without limitation, a three element Er inclusive concentrate available from Tianjio International Trading Co. (U.S.A.), Inc., Burlingame, Calif. (e.g., Yxe2x80x94Hoxe2x80x94Er oxide concentrate), may be used to add the aforesaid lanthanides. This particular concentrate includes, by weight percentage, about 17.27% Y2O3, about 68.29% Er2O3, and about 13.63% Ho2O3 (as well as trace amounts of other elements). Accordingly, in certain preferred embodiments the composition includes at least three times as much Er2O3 as Y2O3. In other embodiments of this invention, two, three or four different lanthanides may be used together with iron to achieve the desired glass color and/or solar characteristics. In certain embodiments of this invention, the wt. % of all lanthanides or rare earth elements (including the lanthanide oxides listed above) in the glass composition put together is from 0.8 to 5.0%, more preferably from 1.0 to 3.0%. In certain preferred embodiments, glass compositions herein have more erbium oxide (Er2O3) than any of holmium oxide (Ho2O3), yttrium oxide (Y2O3), ytterbium oxide, or lutetium oxide taken individually. In certain preferred embodiments, glass compositions herein have at least twice as much erbium oxide (Er2O3) as holmium oxide (Ho2O3). In certain preferred embodiments, glass compositions herein have at least twice as much erbium oxide (Er2O3) as yttrium oxide (Y2O3).